C♯sus4: C♯/D♭ Suspended 4th Piano Chord

Root position: either hand, fingers low note to high
Hand	Notes	Fingers
Right	C♯, F♯, G♯	1-3-5
Left	C♯, F♯, G♯	5-3-1

Scale degree, note, and interval measured from the root.
Degree	Note	Interval from root	Semitones
1	C♯	Perfect unison	0
4	F♯	Perfect fourth	5
5	G♯	Perfect fifth	7

Construction

C♯ Suspended 4th = Root + Perfect 4th + Perfect 5th = C♯, F♯, G♯

Note	Interval	Degree
C♯	Root	1
F♯	Perfect 4th	4
G♯	Perfect 5th	5

Fingering

Note	Key color	Right hand	Left hand
C♯	black	thumb (1)	little finger (5)
F♯	black	middle finger (3)	middle finger (3)
G♯	black	little finger (5)	thumb (1)

Right hand: thumb (1) on C♯, middle finger (3) on F♯, little finger (5) on G♯.

Left hand: little finger (5) on C♯, middle finger (3) on F♯, thumb (1) on G♯.

C♯ Suspended 4th Inversions

Root position
C♯ – F♯ – G♯
1st inversion (C♯sus4/F♯)
F♯ – G♯ – C♯
2nd inversion (C♯sus4/G♯)
G♯ – C♯ – F♯

Key Signature

A Suspended 4th chord is built from symmetrical or ambiguous intervals, so it doesn't belong to a single key and has no key signature of its own.

Chords in the Key of C♯ Major

These are the triads built on each degree of C♯ Major:

I — C♯ Major (major)

Degree	Numeral	Chord	Quality
1	I	C♯ Major	Major
2	ii	D♯ Minor	Minor
3	iii	E♯ Minor	Minor
4	IV	F♯ Major	Major
5	V	G♯ Major	Major
6	vi	A♯ Minor	Minor
7	vii°	B♯ Diminished	Diminished

Scales That Include the C♯ Suspended 4th

A Major (iii)
E Major (vi)
B Major (ii)
F# Major (V)
Db Major (I)
F# Minor (v)
C# Minor (i)
G# Minor (iv)

Same Notes, Other Names

The notes C♯ – F♯ – G♯ aren’t exclusive to this chord. Depending on which note is the bass and how the chord functions, the same pitches also spell:

F♯ Suspended 2nd→

C♯ Suspended 4th : Frequently Asked Questions

What notes are in C♯sus4?

C♯sus4 contains C♯, F♯ and G♯. The formula is 1, 4, 5.

How do you play C♯sus4 on piano?

Play C♯, F♯ and G♯ together. Right hand fingers 1, 3, 5; left hand 5, 3, 1. Every note is a black key.

What are the inversions of C♯sus4?

3 positions: root position C♯ F♯ G♯, C♯sus4/F♯, C♯sus4/G♯.

What is the difference between C♯sus4 and C♯7sus4?

Adds B. 3 of the notes are shared.

What is an easy C♯sus4 for small hands?

The root and third only voicing, C♯3 F♯3, spans 5 semitones or about 69 mm.

What are the frequencies of C♯sus4?

From C♯3 at A440 in 12-TET: 138.59, 185.00, 207.65 Hz.

What is the set class of C♯sus4?

Prime form (027), Forte 3-9, interval vector <010020>.

How do I transpose C♯sus4 to another key?

Keep the 1, 4, 5 formula on the new root. Csus4 is C, F, G; D♭sus4 is D♭, G♭, A♭.

Is D♭sus4 the same as C♯sus4?

Enharmonically yes: the same piano keys and the same sound, spelled differently.

C♯ Suspended 4th in detail

Exact

Every pitch class is present and nothing outside the chord is added.

Type	Notes	Semitones	Span	Omissions and additions	Set relation
Close, root position	C♯3 F♯3 G♯3	7	96 mm	none	identical
Close, first inversion	F♯3 G♯3 C♯4	7	96 mm	none	identical
Close, second inversion	G♯3 C♯4 F♯4	10	138 mm	none	identical
Open, fifth on top	C♯2 G♯2 F♯3	17	234 mm	none	identical

Reduced

A subset of the pitch classes: the identity is incomplete rather than altered.

Type	Notes	Semitones	Span	Omissions and additions	Set relation	Fit
Root and third only	C♯3 F♯3	5	69 mm	omits G♯	subset

Spans are measured centre to centre at a 165 mm octave (standard keyboard geometry).

Position	Bass note	Notes in order	Figured bass	Semitones	Span
Root position	C♯	C♯3, F♯3, G♯3	5/3	7	96 mm
First inversion: C♯sus4/F♯	F♯	F♯3, G♯3, C♯4	6/3	7	96 mm
Second inversion: C♯sus4/G♯	G♯	G♯3, C♯4, F♯4	6/4	10	138 mm

One position per chord tone in the bass. Spans are for close position: voiced inversions appear under Voicings.

Change one note

Chords a single note away, and what moving that note does.

Chord	Change	Formula	Common tones
C♯7sus4	adds B	1 4 5 ♭7	3
C♯	F♯ becomes E♯	1 3 5	2
C♯m	F♯ becomes E	1 ♭3 5	2
C♯sus2	F♯ becomes D♯	1 2 5	2
C♯maj7	F♯ becomes E♯, B♯	1 3 5 7	2
C♯7	F♯ becomes E♯, B	1 3 5 ♭7	2
C♯m7	F♯ becomes E, B	1 ♭3 5 ♭7	2
C♯mMaj7	F♯ becomes E, B♯	1 ♭3 5 7	2
C♯6	F♯ becomes E♯, A♯	1 3 5 6	2
C♯m6	F♯ becomes E, A♯	1 ♭3 5 6	2
C♯add9	F♯ becomes E♯, D♯	1 3 5 9	2
C♯dim	F♯, G♯ becomes E, G	1 ♭3 ♭5	1

Frequencies

Note	MIDI	Frequency
C♯3	49	138.59 Hz
F♯3	54	185.00 Hz
G♯3	56	207.65 Hz

Reference pitch A440, 12-TET, close root position.

Set theory: prime form, Forte number, interval vector

Absolute pitch class set: {1, 6, 8}
Normal order: [6, 8, 1]
Prime form: (027)
Forte number: 3-9
Interval vector: <010020>

Pair	Interval	Semitones	Interval class
C♯ to F♯	Perfect fourth	5	5
C♯ to G♯	Perfect fifth	7	5
F♯ to G♯	Major second	2	2

Where these facts come from

Every value on this page is derived from the note formula for a suspended 4th applied to the root C♯, using standard music theory. Nothing here is hand-entered per chord, so the notes, intervals, inversions and frequencies cannot drift out of agreement with each other. Pitches assume 12-TET at A440.

C♯ Suspended 4th

Fingerings

C♯ Suspended 4th: notes and degrees